Blast during sermon in Iraq mosque kills at least 18

NEW: Sunni lawmaker: Sunni families have recently fled the area because of Shiite militias

The bomb was hidden under a podium from which an imam was speaking, police say

The mosque is in a Sunni village in northeastern Iraq, near a largely Shiite district

There has been a recent uptick in violence, much of it stemming from Sunni-Shiite discord

(CNN) -- A bomb hidden in a Sunni mosque exploded while worshipers listened to a sermon Friday in northeastern Iraq, killing at least 18 people and injuring 56, police and health officials said.

The bomb had been hidden under a podium from which an imam was speaking in the mosque, located in al-Wajihiya in the largely Sunni province of Diyala, said police officials in the nearby provincial capital of Baquba.

Al-Wajihiya is a small Sunni village close to Muqdadiya, a largely Shiite district. It is about 25 kilometers northeast of Baquba, which itself is about 60 kilometers north-northeast of Baghdad.

Over the past few weeks, many Sunni families fled from their houses in small villages close to Muqdadiya because of ongoing threats by Shiite militias, according to a Sunni lawmaker who spoke to CNN on condition of anonymity because of security concerns.

The bloodshed comes amid a recent uptick in violence, much of it stemming from discord between Sunnis and Shiites.

Sunni Arabs had more political clout in Iraq during Saddam Hussein's rule, before his government was deposed in 2003 by the U.S.-led invasion.

Sunnis have long felt politically marginalized under a Shiite-led government in the post-Saddam era.